\startcomponent cpn-overlap
\product opencl-spec-zh

\chapter[appendix:overlap]{CL_MEM_COPY_OVERLAP}

下列代碼描述的是如何確定為 \capi{clEnqueueCopyBufferRect} 指定的源矩形和宿矩形指向了
同一個\cnglo{bufobj}，並且相互重疊。

\startframedtext[%
  style={\ss\tfx},
  width=\textwidth,
]%
\startEnglish
Copyright (c) 2011 The Khronos Group Inc.

Permission is hereby granted, free of charge,
to any person obtaining a copy of this software and /or associated documentation files (the "Materials "),
to deal in the Materials without restriction,
including without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials,
and to permit persons to whom the Materials are furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Materials.

THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM,
OUT OF OR IN CONNECTION WITH THE MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.
\stopEnglish
\stopframedtext

\startclc[style={\tt\tfx}]
bool
check_copy_overlap(size_t src_offset[3],
		size_t dst_offset[3],
		size_t region[3],
		size_t row_pitch, size_t slice_pitch)
{
	const size_t src_min[] = {src_offset[0], src_offset[1], src_offset[2]};
	const size_t src_max[] = {src_offset[0] + region[0],
				src_offset[1] + region[1],
				src_offset[2] + region[2]};

	const size_t dst_min[] = {dst_offset[0], dst_offset[1], dst_offset[2]};
	const size_t dst_max[] = {dst_offset[0] + region[0],
				dst_offset[1] + region[1],
				dst_offset[2] + region[2]};

	// Check for overlap
	bool overlap = true;
	unsigned i;
	for (i=0; i != 3; ++i)
	{
		overlap = overlap && (src_min[i] < dst_max[i])
			&& (src_max[i] > dst_min[i]);
	}
	size_t dst_start = dst_offset[2] * slice_pitch +
			dst_offset[1] * row_pitch + dst_offset[0];
	size_t dst_end = dst_start + (region[2] * slice_pitch +
			region[1] * row_pitch + region[0]);
	size_t src_start = src_offset[2] * slice_pitch +
			src_offset[1] * row_pitch + src_offset[0];
	size_t src_end = src_start + (region[2] * slice_pitch +
			region[1] * row_pitch + region[0]);

	if (!overlap)
	{
		size_t delta_src_x = (src_offset[0] + region[0] > row_pitch) ?
					src_offset[0] + region[0] - row_pitch : 0;
		size_t delta_dst_x = (dst_offset[0] + region[0] > row_pitch) ?
					dst_offset[0] + region[0] - row_pitch : 0;

		if ( (delta_src_x > 0 && delta_src_x > dst_offset[0]) ||
			(delta_dst_x > 0 && delta_dst_x > src_offset[0]) )
		{
			if ( (src_start <= dst_start && dst_start < src_end) ||
				(dst_start <= src_start && src_start < dst_end) )
				overlap = true;
		}

		if (region[2] > 1)
		{
			size_t src_height = slice_pitch / row_pitch;
			size_t dst_height = slice_pitch / row_pitch;
			size_t delta_src_y = (src_offset[1] + region[1] > src_height) ?
						src_offset[1] + region[1] - src_height : 0;
			size_t delta_dst_y = (dst_offset[1] + region[1] > dst_height) ?
						dst_offset[1] + region[1] - dst_height : 0;
			if ( (delta_src_y > 0 && delta_src_y > dst_offset[1]) ||
				(delta_dst_y > 0 && delta_dst_y > src_offset[1]) )
			{
				if ( (src_start <= dst_start && dst_start < src_end) ||
					(dst_start <= src_start && src_start < dst_end) )
					overlap = true;
			}
		}
	}
	return overlap;
}
\stopclc

\stopcomponent

